gentoo-x86/eclass/alternatives.eclass

# Copyright 1999-2003 Gentoo Technologies, Inc.
# Distributed under the terms of the GNU General Public License v2
# $Header: /home/cvsroot/gentoo-x86/eclass/alternatives.eclass,v 1.7 2003/11/24 10:57:06 liquidx Exp $

# Author :     Alastair Tse <liquidx@gentoo.org> (03 Oct 2003)
# Short Desc:  Creates symlink to the latest version of multiple slotted
#              packages.
#
# Long Desc:
#
#  When a package is SLOT'ed, very often we need to have a symlink to the
#  latest version. However, depending on the order the user has merged them,
#  more often than not, the symlink maybe clobbered by the older versions.
#
#  This eclass provides a convenience function that needs to be given a 
#  list of alternatives (descending order of recent-ness) and the symlink.
#  It will choose the latest version if can find installed and create
#  the desired symlink. 
#
#  There are two ways to use this eclass. First is by declaring two variables 
#  $SOURCE and $ALTERNATIVES where $SOURCE is the symlink to be created and 
#  $ALTERNATIVES is a list of alternatives. Second way is the use the function
#  alternatives_makesym() like the example below.
#
# Example:
#  
#  pkg_postinst() {
#      alternatives_makesym "/usr/bin/python" "/usr/bin/python2.3" "/usr/bin/python2.2"
#  }
#
#  The above example will create a symlink at /usr/bin/python to either
#  /usr/bin/python2.3 or /usr/bin/python2.2. It will choose python2.3 over
#  python2.2 if both exist.
#
#  Alternatively, you can use this function:
#
#  pkg_postinst() {
#     alternatives_auto_makesym "/usr/bin/python" "/usr/bin/python[0-9].[0-9]"
#  }
# 
#  This will use bash pathname expansion to fill a list of alternatives it can
#  link to. It is probably more robust against version upgrades. You should
#  consider using this unless you are want to do something special.
# 
ECLASS="alternatives"
INHERITED="$INHERITED $ECLASS"

# automatic deduction based on a symlink and a regex mask
alternatives_auto_makesym() {
        local SYMLINK REGEX ALT myregex
        SYMLINK=$1
        REGEX=$2
        if [ "${REGEX:0:1}" != "/" ] 
        then
                #not an absolute path:
                #inherit the root directory of our main link path for our regex search
                myregex="${SYMLINK%/*}/${REGEX}"
        else
                myregex=${REGEX}
        fi

        # sort a space delimited string by converting it to a multiline list
        # and then run sort -r over it.
        # make sure we use ${ROOT} because otherwise stage-building will break
        ALT="$(for i in $(echo ${ROOT}${myregex}); do echo ${i#${ROOT}}; done | sort -r)"
        alternatives_makesym ${SYMLINK} ${ALT}
}

alternatives_makesym() {
        local ALTERNATIVES=""
        local SYMLINK=""
        local alt pref
        
        # usage: alternatives_makesym <resulting symlink> [alternative targets..]
        SYMLINK=$1
        # this trick removes the trailing / from ${ROOT}
        pref=$(echo ${ROOT} | sed 's:/$::')
        shift
        ALTERNATIVES=$@

        # step through given alternatives from first to last
        # and if one exists, link it and finish.
        
        for alt in ${ALTERNATIVES}; do
                if [ -f "${pref}${alt}" ]; then
                        #are files in same directory?
                        if [ "${alt%/*}" = "${SYMLINK%/*}" ]
                        then
                                #yes; strip leading dirname from alt to create relative symlink
                                einfo "Linking ${alt} to ${pref}${SYMLINK} (relative)"
                                ln -sf ${alt##*/} ${pref}${SYMLINK}
                        else
                                #no; keep absolute path
                                einfo "Linking ${alt} to ${pref}${SYMLINK} (absolute)"
                                ln -sf ${pref}${alt} ${pref}${SYMLINK}
                        fi
                        break
                fi
        done
        
        # report any errors
        if [ ! -L ${pref}${SYMLINK} ]; then
                ewarn "Unable to establish ${pref}${SYMLINK} symlink"
        else
                # we need to check for either the target being in relative path form
                # or absolute path form
                if [ ! -f "`dirname ${pref}${SYMLINK}`/`readlink ${pref}${SYMLINK}`" -a \
                         ! -f "`readlink ${pref}${SYMLINK}`" ]; then
                        ewarn "${pref}${SYMLINK} is a dead symlink."
                fi
        fi              
}               

alternatives_pkg_postinst() {
        if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
                alternatives_makesym ${SOURCE} ${ALTERNATIVES}
        fi              
}

alternatives_pkg_postrm() {
        if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
                alternatives_makesym ${SOURCE} ${ALTERNATIVES}
        fi
}

EXPORT_FUNCTIONS pkg_postinst pkg_postrm

1	liquidx	1.1	# Copyright 1999-2003 Gentoo Technologies, Inc.
2			# Distributed under the terms of the GNU General Public License v2
3	liquidx	1.8	# $Header: /home/cvsroot/gentoo-x86/eclass/alternatives.eclass,v 1.7 2003/11/24 10:57:06 liquidx Exp $
4	liquidx	1.1
5			# Author : Alastair Tse <liquidx@gentoo.org> (03 Oct 2003)
6			# Short Desc: Creates symlink to the latest version of multiple slotted
7			# packages.
8			#
9			# Long Desc:
10			#
11			# When a package is SLOT'ed, very often we need to have a symlink to the
12			# latest version. However, depending on the order the user has merged them,
13			# more often than not, the symlink maybe clobbered by the older versions.
14			#
15			# This eclass provides a convenience function that needs to be given a
16			# list of alternatives (descending order of recent-ness) and the symlink.
17			# It will choose the latest version if can find installed and create
18			# the desired symlink.
19			#
20			# There are two ways to use this eclass. First is by declaring two variables
21			# $SOURCE and $ALTERNATIVES where $SOURCE is the symlink to be created and
22			# $ALTERNATIVES is a list of alternatives. Second way is the use the function
23			# alternatives_makesym() like the example below.
24			#
25			# Example:
26			#
27			# pkg_postinst() {
28			# alternatives_makesym "/usr/bin/python" "/usr/bin/python2.3" "/usr/bin/python2.2"
29			# }
30			#
31			# The above example will create a symlink at /usr/bin/python to either
32			# /usr/bin/python2.3 or /usr/bin/python2.2. It will choose python2.3 over
33			# python2.2 if both exist.
34			#
35			# Alternatively, you can use this function:
36			#
37			# pkg_postinst() {
38			# alternatives_auto_makesym "/usr/bin/python" "/usr/bin/python[0-9].[0-9]"
39			# }
40			#
41			# This will use bash pathname expansion to fill a list of alternatives it can
42			# link to. It is probably more robust against version upgrades. You should
43			# consider using this unless you are want to do something special.
44			#
45			ECLASS="alternatives"
46			INHERITED="$INHERITED $ECLASS"
47
48			# automatic deduction based on a symlink and a regex mask
49			alternatives_auto_makesym() {
50	liquidx	1.6	local SYMLINK REGEX ALT myregex
51			SYMLINK=$1
52	liquidx	1.1	REGEX=$2
53	liquidx	1.6	if [ "${REGEX:0:1}" != "/" ]
54			then
55			#not an absolute path:
56			#inherit the root directory of our main link path for our regex search
57			myregex="${SYMLINK%/*}/${REGEX}"
58	liquidx	1.1	else
59	liquidx	1.6	myregex=${REGEX}
60			fi
61	liquidx	1.8
62	liquidx	1.6	# sort a space delimited string by converting it to a multiline list
63			# and then run sort -r over it.
64	liquidx	1.8	# make sure we use ${ROOT} because otherwise stage-building will break
65			ALT="$(for i in $(echo ${ROOT}${myregex}); do echo ${i#${ROOT}}; done \| sort -r)"
66	liquidx	1.6	alternatives_makesym ${SYMLINK} ${ALT}
67	liquidx	1.1	}
68
69			alternatives_makesym() {
70			local ALTERNATIVES=""
71	liquidx	1.6	local SYMLINK=""
72			local alt pref
73	liquidx	1.8
74	liquidx	1.1	# usage: alternatives_makesym <resulting symlink> [alternative targets..]
75	liquidx	1.6	SYMLINK=$1
76	liquidx	1.8	# this trick removes the trailing / from ${ROOT}
77			pref=$(echo ${ROOT} \| sed 's:/$::')
78	liquidx	1.1	shift
79			ALTERNATIVES=$@
80
81			# step through given alternatives from first to last
82			# and if one exists, link it and finish.
83
84			for alt in ${ALTERNATIVES}; do
85	liquidx	1.6	if [ -f "${pref}${alt}" ]; then
86			#are files in same directory?
87			if [ "${alt%/}" = "${SYMLINK%/}" ]
88			then
89			#yes; strip leading dirname from alt to create relative symlink
90	liquidx	1.8	einfo "Linking ${alt} to ${pref}${SYMLINK} (relative)"
91	liquidx	1.7	ln -sf ${alt##*/} ${pref}${SYMLINK}
92	liquidx	1.6	else
93			#no; keep absolute path
94	liquidx	1.8	einfo "Linking ${alt} to ${pref}${SYMLINK} (absolute)"
95	liquidx	1.7	ln -sf ${pref}${alt} ${pref}${SYMLINK}
96	liquidx	1.1	fi
97			break
98			fi
99			done
100
101			# report any errors
102	liquidx	1.6	if [ ! -L ${pref}${SYMLINK} ]; then
103			ewarn "Unable to establish ${pref}${SYMLINK} symlink"
104			else
105			# we need to check for either the target being in relative path form
106			# or absolute path form
107			if [ ! -f "`dirname ${pref}${SYMLINK}`/`readlink ${pref}${SYMLINK}`" -a \
108			! -f "`readlink ${pref}${SYMLINK}`" ]; then
109			ewarn "${pref}${SYMLINK} is a dead symlink."
110			fi
111	liquidx	1.1	fi
112			}
113
114			alternatives_pkg_postinst() {
115			if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
116			alternatives_makesym ${SOURCE} ${ALTERNATIVES}
117			fi
118			}
119
120			alternatives_pkg_postrm() {
121			if [ -n "${ALTERNATIVES}" -a -n "${SOURCE}" ]; then
122			alternatives_makesym ${SOURCE} ${ALTERNATIVES}
123			fi
124			}
125
126			EXPORT_FUNCTIONS pkg_postinst pkg_postrm
127